The present invention relates to a method and an apparatus for dissolving gases into liquid phases under high pressure, ranging from 2 to 7 atmospheric pressure, in an enclosed pressure vessel. Conventional bubble separation, recarbonation, aeration, and ozonation technologies have a low efficiency for gas dissolution and require a long retention time, and large reactors. The present invention represents a highly efficient alternative to conventional gas dissolution methods in bubble separation, recarbonation, aeration and ozonation reactors.
The Adsorptive bubble separation process (including dissolved air flotation, dispersed air flotation, froth flotation, etc.) is a very effective technology for solid-liquid separation that has been in use outside the environmental engineering field for more than 50 years. Originally applied in the field of mining engineering, adsorptive bubble separation now provides the means for separation and/or concentration of 95 percent of the world's base metals and other mineral compounds. Recently, the adsorptive bubble separation process has become increasingly important in such diverse applications as the separation of algaes, seeds, or bacteria from biological reactors, removal of ink from repulped paper stock, recovery of wool fat from food processing streams, peas from pea pods, coal from slate, gluten from starch, oils from industrial effluents, and more recently in drinking water, cooling water, wastewater, and sludge treatments.
Adsorptive bubble separation process may be defined as the mass transfer of a solid from the body of a liquid, to the liquid surface by means of bubble attachment. The solids are in dissolved, suspended and/or colloidal forms. The three basic mechanisms involved are bubble formation, bubble attachment and solids separation. In general, the light weight suspended solids, such as fibers, activated sludge, free oil, chemical flocs, fats, etc., can be readily separated by the process in accordance with physical-chemical bubble attachment mechanism. The colloidal solids, soluble organics, soluble inorganics, and surface active substances are separated from the bulk liquid by the bubble separation process after they are converted from colloidal or soluble form into insoluble form (i.e. suspended solids) which can then be floated by bubbles.
Alternatively, the soluble surface active substances can be separated easily by an adsorptive bubble separation process in accordance with surface adsorption phenomena. Nonsurface active suspended solids, colloidal solids, soluble organics and soluble inorganics can all be converted into surface active substances. All surface active substances in either soluble form or insoluble form can be effectively floated by fine gas bubbles. Production of fine gas bubbles for bubble separation is a difficult engineering task. Conventional methods and apparatus for the production of fine bubbles is similar to an inefficient pressure spray can, which requires over 2 minutes of detention time and over 50 psig pressure. A high horsepower gas compressor for gas dissolving is a necessity for the conventional gas dissolving system.
Conventional recarbonation, aeration and ozonation processes all involve the use of inefficient porous plates or gas diffusers for the introduction of carbon dioxide gas, air or ozone gas into an aqueous phase under atmospheric pressure and low liquid gravimetric pressure. Since bubble sizes are big and non-uniform, many gas bubbles are not able to completely dissolve into the aqueous phase and one, therefore, wasted in the gas stream. In cases where ozone gas is used, the residual ozone gas in the gas stream may create an air pollution problem.
The present invention is an enclosed highly efficient pressure vessel, including a porous gas dissolving tube and porous gas dissolving plate assemblies which are specifically designed to dissolve air, oxygen, nitrogen, carbon dioxide, ozone, other gases, or combinations thereof into a liquid stream, such as water, under high pressure (2 to 7 atmospheric pressure) and high rotation velocity (over 2,500 rpm). The swirling flow pattern, special nozzles, and porous gas dissolving means combine to achieve 100 percent gas dissolution in liquid and in turn eliminate the problem of a waste gas stream. The detention time needed for gas dissolving is reduced to a few seconds, therefore, the required size of the gas dissolving pressure vessel is significantly reduced. With the new system, a gas compressor becomes a supplemental means for the enhancement of gas dissolving and is no longer absolutely required.